Passive vs. Active Technology
Passive noise-canceling headphones work by blocking noise from reaching your ears. This process involves huge earpieces that entirely cover your ears, combined with thick pieces of foam to insulate your ears from outside noises. This design is called circumaural noise-canceling headphones.
Another popular passive design includes earbuds that actually fit inside your ear, designed to deliver sound directly to your ear canal and block out external sound like earplugs. Unfortunately, passive noise-canceling headphones by themselves are typically not all that effective in actually canceling noises, so many companies combine passive noise-canceling headphones with active noise-canceling technology.
Active noise-canceling headphones use actual noise-canceling technology to reduce noise levels, usually combined with a passive approach to help prevent exterior noise from reaching your ear canals. High-end active noise-canceling technology uses a built-in microphone to monitor environmental noise, and create a counter-frequency to -cancel' the noise.
However, many low-end active noise-canceling headphones don't include the microphone and ability to analyze environmental noise and produce noise-canceling inverse signals, so they simply produce low-level white noise designed to drown out auditory distractions.
Active or Reactive?
Because active noise-canceling headphones work by creating a counter-signal to -block' the undesirable outside noise, you usually experience a slight delay between the headphones detecting noise and the noise-canceling technology blocking it. This means that noise-canceling headphones are most effective at blocking constant noise, such as an airplane, train or car noise, and less effective at intermittent sounds, such as dog barking, babies crying or horns honking.
The Limits of Noise-Canceling Technology
Before you can decide if noise-canceling headphones are worth the price, ask yourself what you want from a pair of noise-canceling headphones. Do you want something to block out most of the outside noise, leaving you with a relatively audible listening experience? Or do you want noise-canceling headphones to surround you in a cone of silence, completely removing you from the outside world and delivering crystal-clear sound? If you're looking for the second option, you're probably not going to be happy with any set of noise-canceling headphones. They can eliminate a lot of outside sound, but even the best noise-canceling headphones can't block out everything.
The Wireless Option
Wireless noise-canceling headphones are another matter entirely. Wireless headphone technology in general isn't up to the level of sound quality provided by corded headphones. Noise-canceling headphones are imperfect. Combine the two, and you have wireless noise-canceling headphones with mediocre sound and mediocre noise-cancellation. You can buy high-end wireless noise-canceling headphones for over $400 that produce reasonable quality results with both audio and noise-canceling, but for the most part, your best bet for wireless noise-canceling headphones is finding a passive, in-ear design.
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How do noise cancelling headphones work? These headsets block out certain frequencies, making it less likely that any offending noises will interrupt your music listening.
How do wireless headphones work? These headphones come in three forms that use three different types of technology: radio, infrared and Bluetooth.